In food, healthcare and agricultural industries, microbial contamination can result in serious disease outbreaks and mass food spoilage ultimately leading to increased mortality, illnesses and costs.
Microbial contaminants may be spread by various means e.g. direct transmission from contaminated surfaces or individuals by touch or through contaminated water supplies. However, in the aforementioned industries even with strict decontamination methods for surfaces, individuals and water supplies in place, microbial contamination still remains commonplace. An aspect of microbial contamination which is far more difficult to control is that of airborne contamination. Microbes may persist on hard to reach surfaces for up to several months or more. When disturbed, these microbes become airborne, enabling transmission to other areas of the particular facility in question. Furthermore, poor compliance with cleaning procedures and high footfall in other areas of a facility may result in regions of high levels contamination. Again, as this area is disturbed by the movement of individuals or machinery, microbial contamination from a low risk' (e.g. warehouse) to a ‘high risk’ (e.g. food production line) area, through airborne contaminants, is likely.
Current methods for assessing the levels of microbial contamination involve the use of (a) sampling and plating, (b) biochemical laboratory analysis and (c) optical methods.
Assessments using methods (a) and (b) usually involve relatively long timescales (several days), dedicated highly trained staff or investment in costly instrumentation and chemicals, or both. For example, samples must be prepared by an individual skilled in the field of microbiology before growing on nutrient media and enumeration or, in the case of polymerase chain reaction (PCR), samples must be isolated and one or a series of chemical preparations performed before the microbes are identified. Therefore, such methods are usually invoked in very specific laboratory analyses.
Prior art proposes the use of optical techniques for the rapid identification of airborne microbes. For example, US patent publication no. 2003/0098422 A1 proposes the use of a UV laser light source to induce auto-fluorescence of compounds in airborne biological matter. However, coherent sources of UV radiation are rather costly and the capacity of these sources to discern differences in signals emitted from bacteria and moulds requires one or more of more complicated equipment, signal processing techniques, or both. It is appreciated that a less costly approach, using widely available technologies and with increased selectivity, represents an attractive alternative to such methods.
Existing optical methods for determining the presence of microbes in optically transparent solids or fluids use the properties of light scattering by microbial species present in the media. For example, US patent publication no. U.S. Pat. No. 6,107,082A discloses an apparatus and process for automated detection of bacteria in a fluid through measurement of the changes in optical density or turbidity of the medium. However, the process requires several preparatory steps which are most suited to supervised laboratory analyses.
U.S. Pat. No. 7,465,560B2 discloses a rapid bacterial detection method based on light scattering by bacterial colonies. The samples are prepared on growth medium and placed in the optical path of a light source. Detectors measure the pattern and intensity of the forward scattered light and the bacterial species are identified by analysis of the unique “fingerprint” of the forward scattered light patterns. However, there is no method proposed for rapid identification of other microbes, for example moulds, or for automatically sampling from the environment.
Prior art demonstrates the applicability of optical scattering methods for rapid identification of microbes. Given the relative simplicity of such methods it is desirable to apply said methods to a fully automated monitoring device, capable of remote sampling and monitoring in, for example, a food production or healthcare facility. Accordingly, the teachings in this document present a viable device for remote sampling and monitoring of microbial activity suitable for use in ambient monitoring applications.